Display unit

ABSTRACT

A display unit comprising a board ( 10 ), a three-primary color-independent optical waveguide ( 100 ) arranged and formed on one side thereof, and a transparent electrode ( 30 ) and an electrode ( 40 ) serving as counter electrodes arranged and formed to sandwich an electric field reaction material ( 20 ) formed on one of two optical waveguides constituting the optical waveguide ( 100 ) and being transparent to waveguide light, wherein part of the waveguide light is allowed to pass at least the field reaction material ( 20 ), and a voltage applied between these counter electrodes changes the shape of the reaction material ( 20 ) to scatter the waveguide light and form pixels in to a displayed image, whereby the device is free from a mechanical drive unit, high in reliability, quality, brightness and response speed, low in power consumption and cost, and capable of full color displaying.

TECHNICAL FIELD

This invention relates to a display device featuring very bright, thinand small-to-large screens, low power consumption and high-speedresponse. It relates especially to a display device that produces animage by scattering guided light by diffusing, expanding, shrinking,deforming, or coloring transparent electroresponsive material containedbetween paired electrodes by applying a voltage between the electrodesat points corresponding to specific pixels.

BACKGROUND OF THE INVENTION

Conventional thin display devices display images by adjusting the lightleaking from the optical waveguide by controlling the contact andseparation of the displacement transmission unit with and from theoptical waveguide using a piezoelectric actuator (see Japanese Laid-OpenPatent Publication Nos. H7-287176, H10-78549 and H11-73142). Also, thereare conventionally proposed systems that leaked evanescent waves bybringing a reflection prism, an extraction unit driven by staticelectricity, close to the optical waveguide (see Japanese Laid-OpenPatent Publication Nos. 2000-75223, 2000-258701 and 2000-330040).

Also an optical switch has been proposed by this inventor that leaksguided light by attracting a cantilever film to the optical waveguide byelectrostatic drive (see Japanese Laid-Open Patent Publication Nos.2001-304537 and 2002-029594).

Additionally, there are conventionally used display units that emit thelight, as pixels, from a back light through a filter of three primarycolors of light and a polarizer using liquid crystal as the opticalshutter. Other conventionally used display devices display pixels byscattering the guided light reflected at the intersurfaces of the glassplates using light-scattering liquid crystal. Liquid crystal is sealedbetween two glass plates to comprise the optical waveguide (see JapaneseLaid-Open Patent Publication No. H11-109349).

Also available were display devices capable of full-color display oflight in three primary colors, which is propagated through an opticalwaveguide, through changes in the refractive index at an optical outputunit provided in the optical waveguide (see Japanese Laid-Open PatentPublication 2000-172197 and U.S. Pat. No. 6,236,799).

However, a problem with the conventional displacement transmission unitdriven by a piezoelectric actuator was the thick piezoelectric elementneeded to transmit a large displacement, resulting in large mass,requiring large drive power, and producing slow response. The systemwith the reflection prism, an electrostatic extraction unit, locatedclose to the optical waveguide has a problem in that its reflectionprism has to have a large mass and is unable to provide high-speedresponse. Further, the electrodes to drive the extraction unit by staticelectricity are almost parallel to each other and are located at adistance through a support, thus requiring large voltage for attraction.Also, the optical switch to leak the guided light by attracting thecantilever thin film to the optical waveguide by static electricity hasa problem in that it needs high voltage for attraction because thecantilever film is isolated from the optical waveguide. Additionally,the system that uses light leakage through the contact part of theabove-mentioned optical waveguide and drive unit has its problems. It isunreliable due to fatigue of its mechanical drive unit, has unexpectedscattering of the guided light due to foreign matter such as duststicking to the core of the optical waveguide which is exposed to theair, and its contact part must be a thick and heavy drive unit to ensurelarge leakage of the guided light and pixels with sufficient brightness.For the above reasons, the advent of reliable (with no mechanical driveunit if possible), bright, highly responsive, and less power-consumingdisplay devices has been anticipated.

A conventional display system using liquid crystal as the opticalshutter has the following problems. It is difficult to see clearly: itvaries greatly depending on the viewing angle because the system emitsthe light from the back light through the liquid crystal and uses apolarizer. Further, it is difficult to produce in thin configurationsbecause it has a complex structure comprising a color filter andpolarizer, and thus has is also expensive.

A display system that seals the light-scattering liquid crystal betweentwo glass plates as the optical waveguide is reliable because it has nomechanical drive unit, but its optical waveguide is two glass plateswith liquid crystal held in between them. It has the following fourproblems.

First, because its optical waveguide is exposed, foreign matter such asdust sticks to its surface, causing the guided light to leak and degradethe quality of the image second, the two glass plates, which are usedalso as the optical waveguide, are the supporting materials and have tobe thick. Thus, it is difficult to form a thin and precise opticalwaveguide. Third, instead of miniaturizing the optical waveguide, thelight of the three primary colors is guided through the same opticalwaveguide, and each pixel is set to scattering mode synchronously withthe light emission, so that the light of the three primary colors canuse the liquid crystal pixel of one point for full-color display. Thissystem needs only one third of the pixels that the conventional methodneeds. But, brightness is necessary to see an image. The shining of onepixel for an instant is too dark. Flickering is large unless thesequentially driven pixels emit light simultaneously. Thus, it isdifficult to get a screen of high brightness with such a system becauseit uses only a transient residual image. Fourth, comprising two glassplates, the board is too hard to provide a flexible image display of thescreen and is vulnerable to impact and damage.

The display device that scatters the light from the initially providedlight output unit by changing the refractive index at the light outputcontrol unit provided in the optical waveguide and by guiding the guidedlight to the light control unit cannot provide a screen of the requiredbrightness. This is because currently available liquid crystals cannotproduce sufficient changes in the refractive index for only a pixel ofabout 100 É m to guide enough light to the light output control unit.

DISCLOSURE OF THE INVENTION

This invention offers display devices capable of monochromic, dichroic,and full-color display, and they feature no mechanical drive unit, highreliability, high quality, high brightness, high-speed response, wideviewing angle, low power consumption, compact and large screens, and atlow cost. To achieve the above objectives, the display device ofinvention first of this patent application is provided with an opticalwaveguide comprising a plate and optical waveguide made of a pair offirst and second optical waveguides, and a transparent electrode and anelectrode arranged and formed so that they are positioned to face inopposite directions while sandwiching an electroresponsive materialformed in the second optical waveguide.

At least one of the first and second waveguides is formed to closely fitthe plate. The first and second optical waveguides are located near orto closely fit each other, so that the light guided to the first opticalwaveguide leaks and works also as the guided light for the secondoptical waveguide. The guided light will be trapped in the First (101)and the second (102) optical waveguides. The electroresponsive material(20) is generally transparent against the guided light, and changes inform when voltage is applied across the transparent electrode (30) andthe electrode (40). The display device is constituted that thescattering of the guided light in the second optical waveguide (102)caused by this change in form emits the scattered light to the outsideas pixels.

First embodiment of this invention states that a transparent plate canbe used as the clad portion of the paired optical waveguide and canserve as the board. The optical waveguide is located at one side of theplate and at least one of the first and second optical waveguides isformed to closely fit the plate, so that the optical waveguide itselfdoes not need to have mechanical strength. Thus, this system is suitablefor arranging several multiple pairs of thin and fine opticalwaveguides.

The first optical waveguide of the pair of optical waveguides can beformed easily, for example, as a projection on the surface of thetransparent plate, a ridge with grooves in both sides of the place wherethe first optical waveguide should be located, with its core prepared bylaminating layers that have a higher refractive index than thetransparent plate, and with clad for the optical waveguide prepared bylaminating layers of low refractive index near one side of the surfaceof the plate and the core embedded in the clad linearly.

Additionally, the second optical waveguide with an electroresponsivematerial between the pair of electrodes is located near or closelyfitted to the top of the first optical waveguide along with thetransparent electrode, and the electroresponsive material is enclosedwith a transparent material having a lower refractive index than itselfto form the clad, so that it serves as the core of the second opticalwaveguide. Thus, the light guided through the first optical waveguide isguided also through the second optical waveguide with its transparentelectrode and electroresponsive material.

When dynamic scattering liquid crystal is used as an electroresponsivematerial, and a voltage is applied across the pair of electrodes untilthe threshold electric field is produced, the material will change inform and become opaque and properly scatter and intensify the lightguided through the second optical waveguide. Thus, the guided light isemitted as scattered light with high brightness to the outside of thetransparent plate of the transparent electrode to be viewed as pixels.

In this case, the pixels emit scattered light and no polarizer isrequired. Thus, this system can offer bright display devices with a wideviewing angle, different from conventional backlit systems with liquidcrystal used as the shutter in combination with the polarizer and colorfilter.

The display device of second invention of this patent application isprovided with an independent two-color optical waveguide, for example, agroup of the optical waveguide for the color red and optical waveguidefor the color green, or an independent optical waveguide for the lightof the three primary colors. A two-color display or a full-color displaycan be made by guiding two colors or three primary colors of lightthrough the corresponding optical waveguides, respectively. For example,two colors of light (red (R) and green (G)), or three primary colors oflight (red (R), green (G), and blue (B)), from a light-emitting diode,laser diode, or organic EL are guided to the corresponding independentoptical waveguide for two colors or for three primary colors, andvoltage is applied to change the form of the electroresponsive materialcontained between the pair of electrodes with the electric field. Acolor display is achieved by scattering the light guided through theoptical waveguide and forming the relevant pixels.

For a full-color display, the three cells in the display unitcorresponding to the three primary colors of light are used as one pixeland the brightness of the light emitted from the pixel, comprising therespective cells, is adjusted by adjusting the intensity of thescattered light with the color image signal according to the degree ofchanges in the form of the electroresponsive material.

When groups of independent optical waveguides for two colors or threeprimary colors are closely arranged to form pixels, contemporarytechnology is applicable for a two-color display or full-color displaysystem to represent the colors of pixels by adjusting the brightness ofthe pixels comprising two colors or three primary colors. These groupsof independent optical waveguides for two colors and three primarycolors are arranged in proper sequence in parallel and linearly to formthe same transparent plate or they are laminated in layers. Further, ofthe independent optical waveguides for the three primary colors, onlythose for two colors may be formed into the same transparent plate. Theplate maybe matched, laminated, and joined in layers with a separateplate formed by the remaining optical waveguides for one color.

The display device of third invention of this patent application guidesthe light from the light source through an optical waveguide that isintegrated with the plate. To construct compact display devices, thelight should preferably be guided through the optical waveguideirrespective of the type of light source: an internal light source suchas a light-emitting diode or laser diode or external light source.

When guiding the light from a light source through an optical waveguideintegrated with the plate, the screen should be made uniform accordingto the size of the display screen, for example, by decreasing the numberof optical waveguides per light source. Certainly, for a large screen,many light sources should be prepared, and their respective dedicatedoptical waveguides and branch optical waveguides should bepredetermined.

The display device of fourth invention of this patent application guidesthe light from the light source through an optical waveguide integratedwith a different plate. Display devices can be constructed, for example,by forming an optical waveguide or by forming only either the firstoptical waveguide or the second optical waveguide, and by joining thewaveguide with the waveguide integrated with a different plate. This hasthe advantage of being easy to form on the plate at least either of thematrix-like pair electrodes and pair cables (verticals election-line andhorizontal selection-line) for the display unit, and drive circuit. Whenone of the pair is formed on one plate, the other should be formed onthe other plate as mentioned above.

Also, with the second optical waveguide of the optical waveguide formedon a transparent plate, part of the optical waveguide integrated on aseparate plate can be used as the first optical waveguide for a displayunit comprising the matrix-like electrode pair arrangement.

The display device of fifth invention of this patent application hasoptical waveguides integrated with a separate plate, with the whole orpart of the surface of the optical waveguides covered with reflectivefilm. The reflective film encloses the light scattered inside theoptical waveguide integrated with a separate plate, so that the lightcan be guided effectively to the optical waveguide.

The display device of sixth invention of this patent application hasscattering materials in the optical waveguide, light-scatteringmaterials, and a lens in the optical waveguide integrated with aseparate plate to guide the light effectively to the optical waveguide.

The light guided from the light source to the optical waveguideintegrated with a separate plate is scattered with the scatteringmaterials in the optical waveguide and irradiated against thelight-scattering materials, and the light-scattering materials areregarded as the second light source. Thus, the light from thelight-scattering materials is the main part of the light guided throughthe lens to the optical waveguide. Thin holographic lenses or convexlenses (depending on the refractive index distribution) should be used.

The display device of seventh invention of this patent application usesa light-emitting diode or laser diode as the light source for theoptical waveguide. These diodes are very stable and can be used as ahighly efficient and long-life light source. Also, because the lightsources are built independently of the display unit comprisingmatrix-like pixels, only good light sources can be selectively installedafter good display devices are built. This ensures extremely high yieldof non-defective display devices.

The display device of eighth invention of this patent application uses alight-emitting diode or laser diode, integrated with the above-mentionedplate or a separate plate, as the light source for the opticalwaveguide. The light source is integrated with the optical waveguidewhich is integrated with a separate plate, thus ensuring a compact andstable display.

The display device of ninth invention of this patent application uses anexternal light source for the optical waveguide. It guides sunlight orthe light from a light bulb to the optical waveguide for display.Because the light source consumes most of the power required for adisplay device, this version uses ambient light in a bright environmentas the light source other than an installed light source for low powerconsumption. The display device may allow switching between internal andexternal light sources.

The display device of tenth invention of this patent application couplesthe light from an external light source with the optical waveguideintegrated with a separate plate using an optical coupler of a ruggedstructure. It effectively couples the light from an external lightsource with the optical waveguide integrated with a separate plate usingan optical coupler of graded ruggedness or Fresnel zone plate or Fresnellens.

The display device of eleventh invention of this patent application usesan external light source as described in the ninth and tenth inventions.For color display, it uses a color filter to change the guided light tothe specific color.

The display device of twelfth invention of this patent application usesplates of which at least either one is of plastic. When using eitherplate as the clad portion, the plate must have a lower refractive indexthan that of the core of the optical waveguide that guides the light.Using both this plate and the other plate of plastic, display devicescan be produced at low cost with display screens that are light inweight, resistant to impact and bending, and in various sizes from smallto large.

The display device of thirteenth invention of this patent applicationuses an electroresponsive material as the light-scattering liquidcrystal. Ferroelectric liquid crystal and twisted nematic liquid crystalcan be used as the light scattering liquid crystal. The light scatteringliquid crystal is transparent when an electric field is not applied toit, and it becomes unstable and opaque when exposed to white light. Whenvoltage is applied across the pair electrodes, sandwiching the liquidcrystal of the above type, until the electric field exceeds thethreshold, the liquid crystal will becomes murky and the light, comingin from the transparent electrode side and being guided, is scatteredthere and emitted outside the transparent plate, thus displaying therelevant portion as the cell of the pixel having the color of the guidedlight of the image. Because the guided light is scattered directly,light-emitting pixels of high brightness are obtained. The brightness ofthe pixels can be adjusted by adjusting the intensity and length of thesignal voltage to be applied to the light-scattering liquid crystal.Certainly, the cell portion of the pixels formed on the opticalwaveguide for red light emits the red light being guided. Also, theoptical waveguides for the blue and green lights emit those lights inthe same manner.

The display device of fourteenth invention of this patent applicationuses an electroresponsive gel as the electroresponsive material. As itgenerally is a high molecular jelly-like gel, the electroresponsive gelchanges its volume by shrinking or expanding when an electric field isapplied to it. This invention scatters the guided light through partialdeformation of the optical waveguide caused by the shrinkage orexpansion of the electroresponsive gel formed between the electrodesunder the voltage applied across the electrodes, which are paired as apixel. Because the electroresponsive gel is jelly-like, the electrodepaired with an transparent electrode moves with the electroresponsivegel in which the electrode pair is formed and which deforms when thevoltage is applied to it caused by the image signal. As it is asemisolid and has no mechanical contact or isolated portions such as acantilever, the gel is free from leakage and easy to handle, although ithas some moving parts.

The display device of fifteenth invention of this patent applicationuses an electroresponsive material as the electrochromic material. Usingoxidation/reduction by the movement of ions in an electrolyte of anelectrochromic material such as tungsten oxide, this invention togglesthe color of the material between colorless to blue or other colors. Thedevice is easy to fabricate using a solid electrolyte as the inorganicmaterial. To use the change in color of an electrochromic material suchas tungsten oxide that changes its color from colorless to blue, thiselectrochromic material and its electrolyte sandwiched between the pairelectrodes (pixels) as the optical waveguide for color development areused. When the electrochromic material is colored, the guided light ofthe same color as the coloring is scattered and emitted outside. To makethe colored material colorless, the voltage applied across the pairelectrodes (pixels) is reversed from that applied when coloring. Thisinvention has the advantage of being able to drive at low voltage,because oxidation/reduction can occur at 1 V or less.

When the display device is used for still images or television, thescreen becomes dark because the time required for light emission is tooshort if the guided light (pixel) is scattered and turned off instantly.To avoid this, the scattered light should continue to be emitted evenwhen the next pixel is selected. The guided light weakens when thescattered light is emitted from the cell units of two or more pixels atthe same time. To avoid this, the power of the light source should beadjusted and the emission time should lengthened depending on the numberof pixels emitting the light at the same time, so that the desireduniform brightness of the pixels can be obtained independently of thenumber of the pixels selected simultaneously.

EFFECTS OF THE INVENTIONS

As explained above, the inventions of this application effectivelyscatter the guided light through changes in form such as by opaquing,deformation, and coloring, by guiding the light through the opticalwaveguide comprising the pair of the first optical wave guide and thesecond waveguide, also through the second optical waveguide generallycontaining transparent electroresponsive materials, and by applying theimage signal voltage across the pair electrodes sandwiching theelectroresponsive materials. Thus, the inventions offer low powerconsuming and high brightness display devices. The inventions of thisapplication can use a transparent plate as the clad portion of theoptical waveguide and also can use it as the supporting board.

The optical waveguide can be arranged and formed on one side of theplate. Thus, the optical wave guide does not need mechanical strength,allows a number of thin and fine optical waveguides to be arrayed inhigh density, and has no mechanical displacement portion, enabling it tooffer small-to-large display devices of high reliability and fine highquality pixel. Also, because the core of the optical waveguide is notexposed, no foreign matter such as dust or dirt will adhere to theoptical waveguide portion of the optical waveguide. Thus, the displaydevices of the inventions of this application can provide optimalperformance even in inferior environments. The main materials of theimage display for the display device such as transparent plates, opticalwaveguide, and clad portion can be made of plastic, which can beflexibly bent mechanically, thus making it possible to offerlight-weight and impact-resistant display devices. Also, because thepixels emit scattered light, the inventions can offer display deviceswith a wide viewing angle, different from conventional devices that usea back light, and liquid crystal combined with the polarizer as anoptical shutter. Also, the display devices of the inventions are capableof not only monochromic display, but also two-color or full-colordisplay by guiding the light of two colors or three primary colorsthrough the corresponding waveguide (100). The display devices transmitthe light from light sources such as light-emitting diodes (LED) andlaser diodes (LD) of three primary colors, red (R), green (G), and blue(B) to the pixel portion through thin optical waveguides. Further, asthey require no polarizer or color filter, the devices can directly emitscattered light to the outside and can be made thin. Thus, the displaydevices of this invention are bright compact and cost-effective. Also,the full-color display devices have independent optical waveguides ofthree primary colors, red (R), green (G), and blue (B), so that therespective waveguides can display pixels made of independent cells forthe three primary colors only. Although they use a sequential drivesystem, the display devices can be adjusted so that, even when the nextpixel portion is selected, the preceding pixel portion can emit light atthe same time. Thus, the display devices are bright, with extremelylittle flickering.

Also, the display devices have the advantage of low power consumption,because they can use not only the internal light source, but also anexternal light source. Also, the pair of the first optical waveguide andthe second optical waveguide that comprise the optical wave guide, andthe pair of the electrode and its wiring that form a matrix-like pixel,can be joined or located closely to each other by forming one of thepair on a plate and the other on a different plate. Thus, the devicescan be assembled using good parts only, thereby raising the yield ofnon-defective components and lowering the prices of the displaysaccordingly.

Further, the optical waveguide is divided into the pair of the firstoptical waveguide and the second optical waveguide that comprise thewaveguide, thereby making the first optical waveguide sufficientlytransparent and bright against the guided light and allowing part of thelight guided through the first optical waveguide to be coupled andpropagated to the second optical waveguide. Thus, this display device issuitable for a large screen even when the second optical waveguide isnot very transparent against the guided light because the guided lightis sufficiently propagated to the first optical waveguide.

The first optical waveguide is a multi-mode waveguide to guide a largeamount of light, and the light is guided at various angles. When thesecond optical waveguide has a lower refractive index than that of thefirst optical waveguide, part of the light propagating through the firstoptical waveguide at a large angle leaks to become the light propagatedthrough second optical waveguide.

When the second optical waveguide has a higher refractive index thanthat of the first optical waveguide, and a layer with a lower refractiveindex is formed between the first optical waveguide and the secondrefractive waveguide (The layer may be an air gap of proximity, liquidcrystal alignment film, or other transparent layer), the second opticalwaveguide acts as having an equivalent lower refractive index. Thus, thesecond optical waveguide is equivalent to an optical waveguide that hasa lower refractive index than the above first optical waveguide.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is the rough sectional view of an embodiment of the full-colordisplay using light-scattering liquid crystal as the electroresponsivematerial, a component of the display device of this invention.

FIG. 1( a) is the horizontal sectional view of the arrangement of theoptical waveguide for the three primary colors.

FIG. 1( b) is the longitudinal sectional view Y—Y in FIG. 1( a) alongthe optical waveguide for the color blue.

FIG. 2 shows the longitudinal sectional views of an embodiment of theoptical waveguide for the color blue, using jelly-like gel that expandsand shrinks under an electric field as the electroresponsive material, acomponent of the display device of this invention.

FIG. 3 shows the rough sectional views of another embodiment of thefull-color display of the display device of this invention.

FIG. 4 shows the longitudinal sectional views of an embodiment along theoptical waveguide for the color blue, using electrochromic material suchas tungsten oxide as the electroresponsive material, a component of thedisplay device of this invention.

FIG. 5 shows an embodiment of the full-color display of this invention.

FIG. 5( a) is the rough horizontal sectional view of the arrangement ofthe optical waveguides 100 r, 100 g, 100 b, for the three primarycolors.

FIG. 5( b) is the enlarged rough view near the optical waveguide 100 rfor the color red.

FIG. 6 is the rough oblique view of an embodiment, showing the mechanismof the full-color display using the light emitted from one pixel 200comprising three cells of the three primary colors, a component of thedisplay device of this invention.

FIG. 7 is an embodiment showing how the light is distributed to theoptical waveguide of each display unit through the respective opticalwaveguides from the LED light source of three primary colors.

FIGS. 7( a) is a rough plan and 7(b) shows horizontal sectional viewsX—X.

FIG. 8 is an embodiment using an external light source. FIGS. 8( a) is arough plan and 8(b) shows horizontal sectional views X—X.

FIG. 9 is the rough sectional view of an embodiment using an externallight source, a component of the display device of this invention.

BEST EMBODIMENTS OF THIS INVENTION

We will explain the display devices of this invention in detail byreferring to Figures. In the FIGS. 10, 11, 12, and 15: plate, 20:electroresponsive material, 25: electrolyte, 30, 30 r, 30 g, 30 b:transparent electrode, 40, 40 r, 40 g, 40 b: electrode, 50: verticalselection line, 60: horizontal selection line, 100, 100A: opticalwaveguide, 100 b: optical waveguide for the color blue, 100 g: opticalwaveguide for the color green, 100 r: optical waveguide for the colorred, 101: first optical waveguide, 102: second optical waveguide, 105:scattering materials in the optical waveguide, 111, 111 r, 111 g, 111 b:taper optical waveguide, 120, 121, 122, 123, 124, 125: clad portion,130, 130 r, 130 g, 130 b: lens, 140, 140 r, 140 g, 140 b:light-scattering material, 150, 150 r, 150 g, 150 b: light source, 200:pixel, 300, 310, 320: reflection film, 400: optical coupler, 450, 450 r,450 g, 450 b: color filter, 500: display.

Embodiment 1

FIG. 1 illustrates an embodiment of the component of the display deviceof this invention using dynamic scattering liquid crystal as theelectroresponsive material 20, and transparent plate 10 as the cladportion 120 of the optical waveguide 100 comprising the pair of thefirst optical waveguide 101 and the second optical waveguide 102. Thecomponent also uses the plate 10 as the supporting board for the thinoptical waveguide 100. In addition, the three primary colors, opticalwaveguide for the color red 100 r, optical waveguide for the color green100 g, and optical waveguide for the color blue 100 b, are arrayedsequentially on both sides of the transparent clad portion 121, so thatthe device is capable of full-color display.

FIG. 1 also illustrates how the electroresponsive material 20 becomesmurky and causes the blue light, or the guided light, to be emittedoutside the transparent plate 10 and observed as a blue pixel. Theelectroresponsive material 20 comprises the liquid-scattering liquidcrystal in the second optical waveguide located between transparentelectrode 30 b and electrode 40 bij, which are the selected pairelectrodes of the optical waveguide 100 b for the color blue.

The principle of operation of the display device of this invention isexplained using FIG. 1 as follows:

FIG. 1( a) is the horizontal sectional view of an embodiment with thearrangement of independent optical waveguides 100 r, 100 g, 100 b forthe three primary colors. In this embodiment, on one side of the plate10, comprising, for example, acrylic plastic and having the action ofthe clad portion 120 and the supporting board to provide the mechanicalstrength of the optical waveguide, are formed the optical waveguide forthe color red 100 r, which is an epoxy core with a large refractiveindex, the optical waveguide for the color green 100 g, and the opticalwaveguide for the color blue 100 b in sequence in the same plane, withthe transparent epoxy clad portion 121 having a small refractive indexinterposed. Along the optical waveguides 100 r, 100 g, 100 b for thethree primary colors, transparent electrodes 30 r, 30 g, 30 b areformed. The transparent electrodes 30 r, 30 g, and 30 b are commonelectrodes, and on the epoxy sheet of the clad portion 123 are formedelectrodes 40 r, 40 g, and 40 b opposing the transparent electrodes atequal pitches in one line. With at least a layer of dynamic scatteringliquid crystal (optical scattering liquid crystal) inserted betweenthese opposing electrodes (pair electrodes) as the electroresponsivematerial 20 in the second optical waveguide 102, the epoxy sheet of theclad portion 123 is coupled with the plate 10.

Generally, nematic liquid crystal has an average refractive index ofabout 1.56, which larger than that (1.48) of ordinary glass. Thus, thelight is easily guided to this liquid crystal layer. The reflection film300 (such as aluminum) is formed by vacuum deposition on the surfaceopposite to electroresponsive material (epoxy sheet) 20 of the cladportion 123. The color image signal voltage is supplied to the selectedelectrode 40 ij among the linearly arrayed electrodes 40 r, 40 g, and 40b, paired to the transparent electrodes 30 r, 30 g, and 30 b, throughthe horizontal selection line 60 formed along the electrodes 40 r, 40 g,and 40 b. The color image signal voltage is supplied to the transparentelectrodes 30 r, 30 g, and 30 b, through the vertical selection line 50(not shown). The simple matrix drive system using contemporarytechnology can be used as the liquid crystal display system. Of course,a active matrix drive system using TFT by means of contemporarytechnology can also be used as the liquid crystal display system.

FIG. 1( b) is the longitudinal sectional view Y—Y in FIG. 1( a) alongthe optical waveguide 100 b for the color blue. Voltage is applied tothe common transparent electrode 30 b formed along the optical waveguide100 b for the color blue in Fig. (a), and to the electrode 40 bij, theblue cell in this specifically selected one pixel in the electrode 40 orlinearly arranged pixels pair to the above common electrode (Thesuffixes ij mean the electrodes, arranged in matrix-like, when line iand row j, specified respectively). In this embodiment, thelight-scattering liquid crystal becomes murky due to the electric fieldthus caused, and the blue light leaked from the first optical waveguide101 and guided to the second optical waveguide 102 of thelight-scattering liquid crystal through the transparent electrode 30 b,is scattered here and emitted outside the transparent plate 10. In afull-color display, the three optical waveguides 100 g for the colorgreen, 100 b for the color blue, and 100 r for the color red, work asone group to perform horizontal and vertical scanning through thehorizontal selection line (60) and vertical selection line (50). Voltageis applied by the color image signal to the transparent electrode 30 andits pair electrode 40 of the groups corresponding to the respectivecolors comprising one pixel in a nearby area. Thus, the respectiveguided lights are scattered by the corresponding light-scattering liquidcrystal and form one pixel comprising a three-color cell for the threeprimary colors.

The contrast or the brightness of the pixel can be adjusted by adjustingthe size of the color image signal voltage and the light scatteringtime. The light scattering time can be adjusted also by applying aquenching pulse such as reverse voltage for light scattering in asuitable time after start of the scattering mode. Light-emitting diodesand laser diodes can be used as the light source for the three primarycolors to offer convenient, compact, and high-brightness displaydevices.

The transparent electrode 30 for the display device of this inventioncan be prepared by sputtering an ITO film or tin oxide film of about0.1–0.3 É m thickness. The electrode 40 can also be made of transparentITO film or tin oxide film, or a non-transparent aluminum that reflectslight as required.

Embodiment 2

FIG. 2 shows the longitudinal sectional views along the opticalwaveguide 100 b for the color blue, using a jelly-like gel(electroresponsive gel) that expands and shrinks under an electric fieldas the electroresponsive material 20 for the display device of thisinvention, as is shown in FIG. 1( b). When a color image signal voltageis applied between the transparent electrode 30 b and the electrode 40ij selected from the electrode 40, paired to the electrode 30 b, theelectroresponsive gel that will become the second optical waveguide 102changes in form (shrinks), decreasing its sectional area. Thus, the bluelight guided there is scattered and emitted outside the transparentplate 10. Gel used as artificial muscle is suitable for theelectroresponsive gel. Transparent polyurethane gel, for example, canalso be used. Epoxy sheet or polyethylene sheet of about 50 É mthickness that deforms easily according to the expansion and shrinkageof the gel can be used as the clad portion 123.

Embodiment 3

Differing from FIG. 1 in Embodiment 1, FIG. 3 shows the horizontalsectional views of an embodiment in which only several opticalwaveguides 100 r for the color red and 100 b for the color blue areformed sandwiching the clad portions 121 on the same plane of the plate10, while the optical waveguide 100 g for the color green is formedperiodically on the clad portion 123 sandwiched by the clad portion 122.Each optical waveguide 100 g for the color green is located between theoptical waveguides 100 r for the color red and 100 b for the color blue.Also in FIG. 3, the image signal voltage over the threshold limit valueis applied to the pair electrodes comprising the transparent electrode30 b and the electrode 40 bij formed on the optical waveguide 100 b forthe color blue. The electric field thus caused makes theelectroresponsive material 20 (Light-scattering liquid crystal layer ofthe second optical waveguide 102) murky and emits the scattered light tothe outside as pixels from the light-scattering liquid crystal layer(Electroresponsive material 20 in the area sandwiched between the pairelectrodes).

FIG. 3 shows a layer provided with the clad portion 122 and opticalwaveguide for the color green 100 g, layer of the electroresponsivematerial 20, layer of pair electrodes, clad portion 124 and reflectionfilm 300: layer of optical waveguide 100 r for the color red and layerof blue pair electrode, clad portion 124 and reflection film 300: layerof optical waveguide for the color red 100 r and optical waveguide forthe color blue 100 b, layer of electroresponsive material 20, layer ofpair electrode, and clad portion 123, laminated and formed on the plate10.

Another embodiment, although not illustrated here, includes, forexample, a layer provided with the clad portion 122 and the opticalwaveguide for the color green 100 g, layer of electroresponsive material20, layer of pair electrode, clad portion 124 and reflection film 300,formed on a separate plate 11 are closely coupled with the laminatedfilms including the optical waveguide for the color red 100 r andoptical waveguide for the color blue 100 b that comprise the opticalwaveguide, thus having almost the same arrangement for that of the threeprimary colors shown in FIG. 3, except for the existence of the plate 11which is different from the plate 10.

Embodiment 4

In FIG. 4, an electrochromic material such as tungsten oxide is used asthe electroresponsive material 20. In the same manner as that shown inFIG. 1( b) for the above Embodiment 1, the transparent electrode 30 b isformed on the optical waveguide 100 b for the color blue and tungstenoxide WO3 is, for example, sputter-deposited as the electroresponsivematerial 20 in the second optical waveguide 102 on the pair electrodesto the above transparent electrode. FIG. 4 shows the sectional view ofthis embodiment with the space between these pair electrodes filled withelectrolyte 25.

Coloring can be toggled between colorless and blue usingoxidation-reduction action by the movement of ions in the electrolyte 25of the electrochromic material such as tungsten oxide. Tungsten oxidechanges from colorless to blue when it is reduced. Thus, when an imagevoltage is applied so that the selected electrode 40 bij side has anegative potential against the transparent electrode 30 b, the tungstenoxide is colored blue. The blue light guided to the point is scatteredat the colored portion and can be seen as blue pixels from outside. Theelectrochromic material can be made easily using a solid electrolyte. Tomake the colored chromic-material colorless, a reverse voltage from thatapplied for coloring is applied to the electrode 40 bij. Because avoltage below 1 V can cause oxidation/reduction, this embodiment can beoperated at low voltage. The coloring of the electrochromic material isbased on electrochemical reaction (change in form). Contrast can beadjusted by the size and application time of the image signal, and thetiming of the return-to-colorless reverse voltage signal. In FIG. 4, theelectrochromic material is formed on only the electrode 40 b as theelectroresponsive material 20. Because its electrical conductivity isnot so high, it may be formed not only on the electrode 40 b, but alsoon the whole surface of the clad portion 123 including the electrode 40b. Also, because the electrochromic material should be present on theelectrode separated for the pixel display, the transparent electrode 30b maybe divided as the pixels without making it a common electrode, andelectrochromic may be formed on only the transparent electrode 30 bclosely, or uniformly including the transparent electrode 30 b.

Embodiment 5

The above embodiment is based on the change in form of theelectroresponsive material 20 in the second optical waveguide 102, andthe image display by the guided scattered light can be observed from theoutside of the transparent plate 10. Obviously, by making the electrode40 transparent and removing the reflection film 300 from the above placeor forming it between the transparent plate 10 and optical waveguide100, or forming it on the outside surface of the plate 10, the imagedisplay can be observed from the optical waveguide 100 side (opposite tothe plate 10). In this case, the plate 10 does not need to betransparent.

FIG. 5 is an embodiment with the reflection film 300 formed between theplate 10 and optical waveguide 100. The plate 10 does not necessarilyneed to be transparent. FIG. 5( a) is an embodiment with independentoptical waveguides for the three primary colors 100 r, 100 g, and 100 b.FIG. 5( b) is an enlargement near the optical waveguide for the colorred 100 r. It shows how the electroresponsive material 20 (The material20 comprises the light-scattering liquid crystal in the second opticalwaveguide 102 contained between the transparent electrode 30 andelectrode 40, which are paired with the cell comprising the pixelselected from the optical waveguide for the color red 100 r) becomesmurky, the guided red light is scattered and taken out as the emissionlight through the transparent electrode 40, reflected also on thereflection plate 300 formed on the plate 10, and observed as a brightred pixel.

In FIG. 5( b), the dynamic-scattering liquid crystal with a highrefractive index serves as the core of the second optical waveguide. Toprevent the bleeding of light to the neighboring optical waveguides, thelight is optically separated with the clad 125 which has a lowerrefractive index than that of the dynamic scattering liquid crystal.

Embodiment 6

FIG. 6 shows how the three primary colors are guided to the dedicatedoptical waveguide and the selected pixel 200 emits the light of thespecified color.

Embodiment 6 has independent optical waveguides for the three primarycolors 100 r, 100 g, 100 b, to which the colors red light R, green lightG, and blue light B are guided, respectively. Voltages corresponding tothe video signals are applied between the selected electrodes 40 r, 40g, 40 b and respective pair transparent electrode 30. Red light R, greenlight G, and blue light B with different light intensities are emittedfrom one pixel 200 comprising the three cells of the three primarycolors to produce a full-color display.

Embodiment 7

FIG. 7 is the display device of this invention for full-color display,showing the arrangement with a focus on the light source 150, opticalwaveguide, and the display unit 500 with the matrix-like electrodearray, and the plate 10. FIGS. 7( a) is the plan view and 7(b) shows thehorizontal sectional view at X—X in 7(a).

The respective lights, emitted from the light sources (red) 150 r,(green) (150 g, and (blue) (150 b) corresponding to the three primarycolors of the light source 150, such as light-emitting diodes (LED), arecoupled with the optical waveguide of thin film 100A and guided, and arethen scattered by the scattering materials in the optical waveguide 105provided in the respective optical waveguide 100A. The lights thenirradiate the scattering materials 140 r, 140 g, and 140 b correspondingto the taper optical waveguides 111 r, 111 g, and 111 b guiding to eachof the optical waveguides 101 r, 101 g, 101 b under the display unit 500in each optical waveguide 100A.

The light scattering materials 140 r, 140 g, and 140 b work just likethe respective second light sources, and they are converged throughfilm-like lenses 130 r, 130 g, and 130 b corresponding to 140 r, 140 g,and 140 b, and then guided to each optical waveguide 100. In FIG. 7, twoeach of the light sources 150 of the same color are provided for theoptical waveguide 100A corresponding to each of the three primarycolors, to produce pixels with high brightness.

In this embodiment, the optical waveguide 100A is covered with thereflection film 320 and the reflection film 310 is provided on the endsurface of each optical waveguide 100. The display unit 500 also has theplate 10 with the reflection film 300 formed on it, to prevent theleakage of display pixels other than those selected, thereby maintainingbrightness inside the optical waveguide 100.

Embodiment 8

FIG. 8 is the display device of this invention for a full-color displayand is the same as the embodiment shown in FIG. 7, except that theoptical coupler 400 to use external light sources and the color filters450, 450 r, 450 g, and 450 b to obtain the three primary colors areprovided instead of the three primary colors 150 r, 150 g, 150 b (150 inFIG. 7). FIG. 8( a) is a plan view. FIG. 8( b) is a horizontal sectionalview. The optical waveguides 110A for the colors red and blue providedwith optical coupler 400 are inverted from the embodiment shown in FIG.7.

Optical coupler 400 can be conveniently made from plastic usingfilter-like or rugged diffraction grating, or a Fresnel lens.

The light from an external light source is converted into the threeprimary colors through the optical coupler 400 and color filters 450 r,450 g, and 450 b, then passes through respective optical waveguides 100,and is guided to the optical waveguide 100A in the same manner as shownin Embodiment 7.

The optical coupler 400, color filter 450, and built-in light source 150such as LED may be provided as required, although they are notillustrated here. The optical shutter 400 should be provided with ashutter for switching.

Embodiment 9

FIG. 9 is the horizontal sectional view of an embodiment of the displaydevice of this invention. The light source for the three primary colors150 and optical waveguide 100A are arranged in the same manner as thatof the embodiment in FIG. 7, except that they are pre-formed on theplate 15 and one of the pair matrix-like electrodes is formed on thetransparent plate 10 together with the second optical waveguide 102. Onthe plate 15, are formed the first optical waveguide 101 of the opticalwaveguide 100 and its counterpart of the pair electrode. The firstoptical waveguide 101 is integrally coupled with the second opticalwaveguide 102 formed on the plate 10, making up the display unit 500comprising matrix-like pair-electrode pixels. In this embodiment, thefirst optical waveguide 101 is part of the optical waveguide 100Aintegrated in the plate 15. Because the reflection film 300 is formed inthe plate 15, the plate does not need to be transparent. Instead, theplate 10 is transparent so that the image is displayed from the top ofthe plate 10.

Obviously, when the reflection film 300 of the embodiment in FIG. 9 isformed on the side of the plate 10 of the display unit 500, the plate 10may be non-transparent, and the image can be viewed from the plate 15side if the plate 15 is transparent and a transparent electrode is used.

Regarding the optical waveguide 100A integrated in the plate 15 of thisembodiment shown in FIG. 9, the display device of this invention canalso be constituted by forming the first optical waveguide 101 and thesecond optical waveguide 102 of the optical waveguide 100 on the plate10 in advance, and closely coupling the first optical waveguide 10l withthe optical waveguide 100A.

Also, the optical waveguide 100 maybe constituted as pair by couplingclosely or proximately the first optical waveguide 101, pre-formed onthe plate 10, with the second optical waveguide 102, formed in a thirdplate 12, different from the plates 10 or 15. In this case, one of thepair of the transparent electrode 30 and electrode 40 pair used tocomprise a pixel, and the pair wiring, can be formed on the plate 10 andthe other on 12. Additionally, an electroresponsive material 20 such asdynamic scattering liquid crystal should be inserted between the pairelectrodes and used as the core for the second optical waveguide 102.

Although the above embodiment does not show the matrix-like pairelectrodes, pair wiring (vertical selection line 50 and horizontalselection line 60), nor their drive circuit, the wiring for the pairelectrodes should be formed on the optical waveguide 100 or either ofthe flattened first optical waveguide 101 or the second opticalwaveguide 102, and should be extended outside the optical waveguide 100and formed on the plate 10 or 15 together with the drive circuit. In theembodiment shown in FIG. 9, the complexity of the optical waveguide 100Aintegrated on the plate 15 can be conveniently avoided by forming thewiring and drive circuit on the plate 10. As shown in FIG. 9, one of thepair of the matrix-like electrodes and wiring is formed on the plate 15and the other on the plate 10. Because the pair wirings cross at rightangles to each other, the pair wirings can be extended to a free area onthe surface of the plates 15 and 10, without the first optical waveguide100A or the second optical waveguide 102 formed on them. Thus, the pairwirings can be formed closely and directly on the plates 15 and 10,enabling easy-to-build and stable display devices.

In the above embodiment, the pair electrodes and wiring are arranged andformed so that voltage is applied, even when it is applied through thealignment layer, almost directly to the electroresponsive material 20such as the liquid crystal in the second optical waveguide 102, which isone of the components of the optical waveguide 100. However, directapplication of voltage is not necessarily required. Considering that thefirst optical waveguide 101 has thickness and some electricconductivity, one of the pair of the electrode and wiring may be formedoutside the first optical waveguide, so that voltage is applied acrossthe first optical waveguide 101 and the second waveguide 102.

If for the waveguide light source 150, for example, one blue LED is notsufficiently bright, two or more LEDs can be optically coupled with thecorresponding optical waveguide 100A and they can be turned onsimultaneously.

The above embodiments are only examples of the embodiments, and othervariations with the same objectives, operation, and effects as those ofthis invention may exist.

INDUSTRIAL APPLICABILITY

As explained above, as they have no mechanical driving unit, the displaydevices of this invention are reliable, offer fine high-quality pixels,high brightness, high-speed response, emit scattered light from thepixels, and require no polarizer. Thus, differing from conventionaldisplay devices, which use a back light and the liquid crystal as theoptical shutter in combination with the polarizer and color filter, thedisplay devices of this invention also feature a wide viewing angle,brightness, low power consumption, compact and large screens, low cost,and monochromic, dichroic, and full-color display. Also, the displaydevices of this invention offer high-quality images even in an adverse,e.g., dusty, environment because the core of its optical waveguide isnot exposed and is free from foreign matter. Also, the display devicesare flexible and easily bent mechanically because the transparent plate,optical waveguide, and clad portion, which are the main components ofthe image display unit of the display device, can be made of plastic.Thus, the display devices of this invention are light in weight andimpact-resistant, and have a wide range of industrial applications thatrequire display devices.

1. A display device comprising: a first plate, a paired opticalwaveguide comprising a first optical waveguide and a second opticalwaveguide, a first transparent electrode, and a second electrode whichfaces the first transparent electrode, the second optical waveguidecomprising an electroresponsive material formed between the firsttransparent electrode and the second electrode which face each other,wherein at least one of the first optical waveguide and the secondoptical waveguide is formed in close contact with the first plate, andthe first and second optical waveguides are disposed in close contactwith or near each other so that light guided to the first opticalwaveguide is led to and leaks through the second optical waveguide, andwherein the electroresponsive material is transparent against the guidedlight, but changes in form when voltage is applied between the firsttransparent electrode and the second electrode to thereby scatter theguided light of the second optical waveguide and emit the scatteredlight outside as pixels.
 2. The display device according to claim 1,wherein the paired optical waveguide comprises groups of independentoptical waveguides for two colors or three primary colors, so that thedisplay device displays two colors or three colors by guiding the twocolors or the three primary colors through the corresponding opticalwaveguides.
 3. The display device according to claim 1, wherein lightfrom a light source is guided to the paired optical waveguide through anoptical waveguide integrated on the first plate.
 4. The display deviceaccording to claim 1, wherein light from a light source is guided to thepaired optical waveguide through an optical waveguide integrated on asecond plate which is different from the first plate.
 5. The displaydevice according to claim 3, wherein part or a whole of a surface of theoptical waveguide integrated on the first plate is covered with areflection film.
 6. The display device according to claim 3, wherein afirst scattering material, a second light-scattering material, and alens are provided in the optical waveguide integrated on the first plateso as to efficiently guide the guided light to the paired opticalwaveguide.
 7. The display device according to claim 1, wherein a lightsource provides a guided light to the paired optical waveguide, andwherein said light source is a light-emitting diode or a laser diode. 8.The display device according to claim 1, wherein a light-emitting diodeor a laser diode is integrally formed on the first plate or on a secondplate which is different from the first plate.
 9. The display deviceaccording to claim 1, wherein an external light source other than thedisplay device is used to provide a guided light to the paired opticalwaveguide.
 10. The display device according to claim 9, wherein lightfrom the external light source is led to the optical waveguideintegrated on the first plate, using an optical coupler having a ruggedstructure.
 11. The display device according to claim 9, wherein a colorfilter is provided to change color of the guided light to a specificone.
 12. The display device according to claim 4, wherein at least oneof the first and second plates is made of plastic.
 13. The displaydevice according to claim 1, wherein the electroresponsive material isused as light-scattering liquid crystal.
 14. The display deviceaccording to claim 1, wherein the electroresponsive material is gelwhich expands or shrinks when voltage is applied.
 15. The display deviceaccording to claim 1, wherein electrochromic material is used as theelectroresponsive material.
 16. The display device according to claim 4,wherein part or a whole of a surface of the optical waveguide integratedon the second plate is covered with a reflection film.
 17. The displaydevice according to claim 4, wherein a first scattering material, asecond light-scattering material, and a lens are provided in the opticalwaveguide integrated on the second plate so as to efficiently guide theguided light to the paired optical waveguide.
 18. The display deviceaccording to claim 1, wherein a light-emitting diode or a laser diode isintegrally formed on the first plate or on a second plate which isdifferent from the first plate.
 19. The display device according toclaim 2, wherein light from a light source is guided to the pairedoptical waveguide through an optical waveguide integrated on the firstplate.
 20. The display device according to claim 2, wherein light from alight source is guided to the paired optical waveguide through anoptical waveguide integrated on a second plate which is different fromthe first plate.